Glass grinding apparatus



Oct. 29, 1935. F. B. WALDRON GLASS GRINDING APPARATUS Filed Feb. 8, 1955 Patented Oct. 29, 1935 [TED STATES PATENT OFF! GLASS GRINDING APPARATUS Frederic Barnes Waldron, Prescot, England, assignor to Pilkington Brothers Limited, Liverpool, England, a company of England Application February 8,1935, Serial'No. 5,508

6 Claims.

surface on the glass and to grind more efficiently.

The operative surface of grinding tools, used in a continuous grinding machine on a travelling strip of glass, and supplied with abrasive at the centre of the tools, is commonly composed of the surfaces of blocks, formed by two sets of grooves, one set leading the abrasive outwardly from the centre, while the other set is circular, and concentric with the axis of the tool.

The outwardly leading grooves serve to enable abrasive supplied at the centre to reach the outer parts of the tool, and the circular grooves serve for the renewal of the spent abrasive. When a quantity of abrasive reaches the operative surface of the block, it travels to the outer edge of this block while performing grinding work. After doing a certain amount of grinding, it loses its efilciency as an abrasive. Its path from the inner to the outer edge of the block, that is to say, from one circular groove to the next, is such that, before the abrasive becomes spent, it reaches a circular groove and there becomes mixed with fresh abrasive, so that fresh abrasive reaches the operative surface of the next block outwards.

In the following specification, grooves serving mainly to lead the abrasive outwardly will be termed spreading grooves, and grooves serving mainly to provide fresh abrasive will be termed mixing grooves. Thus, in the ordinary form of grinding tool, the spreading grooves are radial and the mixing grooves circular.

Now the glass produced by grinding tools of the above described customary form, is sufficiently flat for many commercial purposes, but certain irregularities in flatness are produced which render the glass unsuitable for certain purposes.

If the annular grinding surface be regarded as divided up into narrow concentric rings, it has been found that irregularities in flatness are produced when the area of grinding surface in any one ring differs largely from that in the adjacent rings.

Now the condition that the area of grinding surface in any one ring should not differ largely from that in the adjacent rings can be fulfilled by making the mixing grooves elliptical or eccentric, with suitable eccentricity. A grinding tool with such grooves, however, is found to grind unevenly for the reason that the abrasive becomes unevenly distributed round the elliptic or eccentric grooves, being driven by centrifugal force to the portions of the grooves at greater radii.

The above mentioned condition is also fulfilled by the known form of tool with spreading grooves {5 only, whether radial or inclined to the radius. In this form of tool, however, the grinding has been found to be inefficient by reason of the abrasive being driven by centrifugal force too readily to the rim, when the grooves are radial, 10

or nearly so, and, when they are inclined, by reason of its having too long a path before reaching an adjacent groove.

According to the invention, a disc grinding tool for operating on travelling flat glass has its op- 1557 erative surface broken up by grooves reaching from the central space to points near the periphery, the grooves having a plurality of portio-ns inclined to the radius by an angle greater than 45, the inclination being such that the outer ends of such portions are in advance (having reference to the direction of rotation) of their inner ends. The grooves are preferably wider at the operative surface than at the bottom, at least in the said inclined portions, the greater width being given by inclination of their trailing walls. The said portions may be straight or curved, and each groove may consist entirely of curved portions. The inclination to the radius of the said inclined portions preferably increases V with increasing radius.

In the accompanying drawing:

Figures 1, 2 and 3 are each plan views of the operative surface of one-quarter of a grinding tool, showing alternative forms of the invention on a single disc, and

Figure 4 is a plan view of a portion of Figure 2, showing an alternative form of groove.

The disc I with central hole 2, through which abrasive is supplied, rotates in the direction of the arrow and has formed in it grooves 3, reaching from the central space 4 to points 5 near the periphery. Referring to Figure 1, each groove 3 has a short inner radial portion 6, then a portion 1 inclined to the radius at about 70, then another short radial portion 8, then a portion 9 inclined to the radius at about 75, then another short radial portion I0 and finally a portion ll inclined to the radius at about 80".

Referring to Figure 2, each groove 3 has three straight portions I2 inclined to the radius at about 25, alternating with curved portions [3, l4 and I5 at average inclinations to the radius of about and respectively.

Referring to Figure 3, each groove 3 is of the same general form as the grooves in Figure 2, but is curved into a wavy form throughout.

Figure 4 shows the inner portion of the groove marked 3' in Figure 2, but so formed as to be wider at the operative surface than at the bottom, the greater width being given by inclining the trailing wall as at Hi, This form of groove is of advantage in tools operating on the under surface of a strip of glass, since, as explained in my Patent No. 1,956,781, the abrasive is forced upwards to the operative surface by reason of the inclination of the wall l6 together with the inclination of the groove.

Having described my invention I declare that what I claim and desire to secure by Letters Patent is:-

1. Disc grinding tool for operating on travelling fiat glass, grooves in the operative surface thereof of general zig-zag form reaching from the central space to points near the periphery, and having a plurality of portions which produce leading faces of the operative surface inclined to the radius by angles between forty-five and seventy degrees near their inner ends and between fifty and eighty degrees near their outer ends, the inclination being such that the outer ends of such portions are in advance (with reference to the direction of rotation) of their inner ends,

2. Disc grinding tool for operating on travelling fiat glass, grooves in the operative surface thereof of general zig-zag form reaching from the central space to points near the periphery, and having a plurality of portions which produce leading faces of the operative surface inclined to the radius by angles between forty-five and seventy degrees near their inner ends and between fifty and eighty degrees near their outer ends, the inclination being such that the outer ends of such portions are in advance (with reference to the direction of rotation) of their inner ends, and other portions alternating with the said portions inclined to the radius in the same direction but to a lesser degree.

3. Disc grinding tool for operating on travelling fiat glass, grooves in the operative surface thereof of general zig-zag form reaching from the central space to points near the periphery and having a plurality of portions which produce leading faces of the operative surface inclined to the radius by angles between forty-five and seventy degrees near their inner ends and between fifty and eighty degrees near their outer ends, the inclination being such that the outer ends of such portions are in advance (with reference to the direction of rotation) of their inner ends, and radial portions alternating with the said portions.

4. Disc grinding tool for operating on travelling flat glass, wavy grooves in the operative surface thereof of general zig-zag form reaching from the central space to points near the periphery having a plurality of portions which produce leading faces of the operative surface inclined to the radius by angles between f orty-five and seven ty degrees near their inner ends and between fifty and eighty degrees near their outer ends, the inclination being such that the outer ends of such portions are in advance (with reference to the direction of rotation) of their inner ends.

5. Disc grinding tool for operating on travelling flat glass, grooves in the operating surface thereof of general zig-zag form reaching from the central space to points near the periphery, and having a plurality of portions which produce leading faces of the operative surface inclined to the radius by angles between forty-five and seventy degrees near their inner ends and between fifty and eighty degrees near their outer ends, the inclination being such that the outer ends of such portions are in advance (with reference to the direction of rotation) of their inner ends, the grooves being Wider at the operative surface than at the bottom, the greater width being given by inclination of their trailing walls.

6. Disc grinding tool for operating on travelling flat glass, wavy grooves in the operative surface thereof of general zig-zag form reaching from the central space to points near the periphery, having a plurality of portions which produce leading faces of the operative surface inclined to the radius by angles between forty-five and seventy degrees near their inner ends and between fifty and eighty degrees near their outer ends, the inclination being such that the outer ends of such portions are in advance (with reference to the direction of rotation) of their inner ends, the grooves being Wider at the operative surface than at the bottom, the greater width being given by inclination of their trailing Walls.

FREDERIC BARNES WALDRON. 

